Author Archives: TKH Specialist
Password Recovery in Redhat 7
- Feb
- 11
Forgot your password on your rhel7 server? Well there are some differences to process from rhel6. Here is how you do it. With SELinux and systemd in the mix we have to deal with that. Here is the procedure of what needs to be done in order to recover a forgotten root password on Redhat […]
read moreWhen did that change?
- Feb
- 09
Trying to shutdown an old web server from the late 1990’s that had it’s guts transplanted onto a newer system around 2003 and again around 2009. As you can imagine there are accounts and files that are like those items in your junk drawer, they beg the question…why is this here?! In an attempt to […]
read moreSubnet Mask Cheat Sheet
- Nov
- 09
Here is a “Subnet Mask Cheat Sheet” since I don’t have to remember this that often any more. Information found also via RFC 1878. Addresses Hosts Netmask Amount of a Class C /30 4 2 255.255.255.252 1/64 /29 8 6 255.255.255.248 1/32 /28 16 14 255.255.255.240 1/16 /27 32 30 255.255.255.224 1/8 /26 64 62 255.255.255.192 […]
read moreDisk Woes
- Sep
- 10
I hope to never use this document again but thought it worth documenting in case someone else has need of the information. I powered my desktop off for a planned power outage. When I powered it back on the system failed to boot reporting either “Error 17” or “Error 25”, in short the software raid […]
read moreUnresponsive VMware Images
- Sep
- 10
Over the past week I have had two vmware images become unresponsive. When trying to access the images via the vmware console any action reports: rejecting I/O to offline device A reboot fixes the problem, however for a Linux guy that isn’t exactly acceptable. Upon digging a little deeper it appears the problem is with […]
read moreTo reboot or not to reboot?
- Jun
- 10
You have patches to apply, we all know that if there are kernel patches that you need to (or at least should) restart/reboot the server. But what about other packages? There are a few non-kernel patches which can cause havoc if you spply them and do not reboot the server. The biggest package that most […]
read morescreen your work…
- May
- 27
The Linux screen command is a very useful tool for many reasons. For one you don’t need to worry about losing your session. Sometimes long running jobs with little or no output can lead to your remote session terminating, not usually a helpful thing. Other benefits of the screen command are session logging (thing documentation) […]
read more6GB free = 100% disk usage?!
- May
- 15
What to do when you have plenty of available disk space but the system is telling you the disk is full?! I was working on a server migration, moving 94GB of user files from the old server to the new server. Since we aren’t planning on seeing a lot of growth on the new server, […]
read moreCleaning Up Memory Usage
- May
- 06
I noticed my Ubuntu desktop was using a rather large portion of available memory. I usually have a lot running on my system, multiple terminals, background jobs, etc so this is nothing unusual. Today however I noticed my system was sluggish so I started digging. Memory use was near 100%. I closed all of my […]
read morevi & vim aids
- Apr
- 10
For my quick reference. To open two files in vi/vim and edit side by side (use CTRL-W + w to switch between the files): # vim -O foo.txt bar.txt To open a file and automatically move the cursor to a particular line number (for example line 80) # vi +80 ~/.ssh/known_hosts To display line numbers along the […]
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